With the rapid rise in demand for communication of large amounts of data to and from mobile communication devices, traditional mobile voice communication networks are evolving into networks that communicate with Internet Protocol (IP) data packets. Such IP data packet communication can provide users of mobile communication devices with voice over IP, multimedia, multicast and on-demand communication services.
An exemplary network structure for which standardization is currently taking place is an Evolved Universal Terrestrial Radio Access Network (E-UTRAN). The E-UTRAN system can provide high data throughput in order to realize the above-noted voice over IP and multimedia services. The E-UTRAN system's standardization work is currently being performed by the 3GPP standards organization. Accordingly, changes to the current body of 3GPP standard are currently being submitted and considered to evolve and finalize the 3GPP standard.
Furthermore, EU started the METIS project in November 2012 to lay the foundation of 5G, the next generation mobile and wireless communications system. The main technical objectives (or 5G requirements) include the following:                1000 times higher mobile data volume per area;        10 to 100 times higher number of connected devices;        10 to 100 times higher user data rate;        10 times longer battery life for low power massive machine communications (MMC); and        5 times reduced End-to-End latency (<5 ms).        
It is clear the above requirements demand much higher system capacity than what can be offered by the legacy systems. Thus, a new radio access technology can be expected to fulfill these requirements.